apsides

apsides

The satellite's orbit reaches its apsides at the farthest and nearest points from the planet.

Definition
  1. Noun (plural of ):
    • Astronomy: The two points in an orbit (of a celestial body, such as a planet or satellite) that are nearest to and farthest from the central body (e.g., the Sun or Earth). The nearest point is called the periapsis (or perigee for Earth), and the farthest point is called the apoapsis (or apogee for Earth).
    • Architecture: In ancient architecture, an apsis (plural apsides) refers to a semicircular or polygonal recess, often in a church or basilica, typically containing an altar.
Usage Examples

  • Astronomy:

    • The orbit of the Moon has two apsides: the perigee and the apogee. (The closest and farthest points from Earth in the Moon’s orbit.)
    • Calculating the apsides of a comet helps predict its visibility from Earth. (The points of nearest and farthest approach to the Sun.)

  • Architecture:

    • The Romanesque church featured two apsides on either side of the nave. (Semicircular recesses in the building structure.)
Advanced Usage

  • "line of apsides": The imaginary line connecting the two apsides of an orbit, passing through the central body.

    • The line of apsides rotates slowly over time due to gravitational perturbations. (The axis connecting the nearest and farthest orbital points.)

  • "apsidal precession": The gradual rotation of the line of apsides over time, a phenomenon observed in planetary orbits.

    • Mercury exhibits significant apsidal precession, which helped confirm Einstein’s theory of general relativity. (The slow turning of the orbital axis.)
Variants and Related Words

  • Apsis (noun, singular): One of the apsides.

    • The apsis of the planet’s orbit was calculated with great precision. (A specific point of nearest or farthest approach.)

  • Apsidal (adjective): Relating to an apsis or apsides.

    • The apsidal distance varies depending on the eccentricity of the orbit. (The distance at the apsidal points.)
Synonyms
  • Orbital extremities: the extreme points of an orbit.
  • Turning points: the points where the orbital motion changes direction relative to the central body.
Related Idioms